The location of a mobile, wireless or wired device is a useful and sometimes necessary part of many services. The precise methods used to determine location are generally dependent on the type of access network and the information that can be obtained from the device. For example, in wireless networks, a range of technologies may be applied for location determination, the most basic of which uses the location of the radio transmitter as an approximation.
Exemplary wireless networks may be a World Interoperability for Microwave Access (“WiMAX”) network, a Long Term Evolution (“LTE”) network, and the like. Generally, WiMAX is intended to reduce the barriers to widespread broadband access deployment with standards-compliant wireless solutions engineered to deliver ubiquitous fixed and mobile services such as VoIP, messaging, video, streaming media, and other IP traffic. LTE is generally a 4G wireless technology and is considered the next in line in the Global System for Mobile Communication (“GSM”) evolution path after Universal Mobile Telecommunications System (“UMTS”)/High-Speed Downlink Packet Access (“HSPDA”) 3G technologies. LTE builds on the 3GPP family including GSM, General Packet Radio Service (“GPRS”), Enhanced Data Rate for Global Evolution (“EDGE”), Wideband Code Division Multiple Access (“WCDMA”), High Speed Packet Access (“HSPA”), etc., and is an all-IP standard like WiMAX. LTE is based on orthogonal frequency division multiplexing (“OFDM”) Radio Access technology and multiple input multiple output (“MIMO”) antenna technology. LTE provides higher data transmission rates while efficiently utilizing the spectrum thereby supporting a multitude of subscribers than is possible with pre-4G spectral frequencies. LTE is all-IP permitting applications such as real time voice, video, gaming, social networking and location-based services. LTE networks may also co-operate with circuit-switched legacy networks and result in a seamless network environment and signals may be exchanged between traditional networks, the new 4G network and the Internet seamlessly. While LTE protocol is being defined in the 3GPP standards as the next generation mobile broadband technology, there is a need for mobile subscriber or user equipment (“UE”) location in exemplary networks for compliance with the FCC E-911 requirements and for other location based services. The 3GPP standards have also identified different methods that could be used for positioning of an UE for an evolved-UMTS Terrestrial Radio Access Network (“E-UTRAN”).
A number of applications currently exist within conventional communication systems, such as those supporting GSM, Time Division Multiple Access (“TDMA”), Code Division Multiple Access (“CDMA”), Orthogonal Frequency Division Multiple Access (“OFDMA”) and UMTS technologies, for which location solutions are needed by mobile units, mobile stations, UE or other devices and by other entities in a wireless network. Examples of such applications may include, but are not limited to, GPS positioning and assisted global position system (“A-GPS”) positioning. A-GPS adaptable UE may acquire and measure signals from a number of satellites to obtain an accurate estimate of the UE's current geographic position. GPS-based solutions may offer excellent accuracy, but GPS-based solutions generally suffer from yield issues in indoor environments or in environments that provide a poor line of sight to the open sky in which to best receive GPS satellite transmissions. Furthermore, embedding GPS chipsets into UE may also add an associated cost to the manufacturing of the UE and an associated cost to A-GPS functionality in the respective communications network. There, however, exists a need in the art to locate UMTS, OFDMA or W-CDMA mobile devices to satisfy FCC E-911 regulations as well as to provide Location Based Services for mobile phone users.
The 3GPP UMTS standard outlines several methods for location including Cell-ID, Enhanced Cell-ID (“E-CID”), A-GPS, Observed Time Difference of Arrival (“OTDOA”), and Uplink Time Difference of Arrival (“U-TDOA”). Cell-ID generally is the simplest method which provides coarse positioning of mobile devices based on a known location of the coverage area centroid of each base station sector. Additionally, A-GPS is a straightforward implementation for network and handset manufacturers due to their legacy in CDMA2000 networks. Likewise, U-TDOA is also a straightforward technique for those skilled in the art and has been widely deployed for other air standards. OTDOA may be confronted with significant implementation challenges for network carriers, due to the fact that the base station timing relationships must be known, or measured, for this technique to be viable.
Some prior art systems are mobile appliance-based and determine the position of the mobile appliance by receiving multiple dedicated location signals either from components outside the mobile appliance's communication system, such as satellites and GPS systems or from a network of dedicated land-based antennas. Other prior art geolocation systems that are network overlay, or infrastructure-based, systems use combinations of specific, as opposed to ambiguous, measurements generally from multiple base stations, such as AOA, TOA and TDOA. These specific measurement values may be utilized to solve a set of mathematical equations to determine the location of the mobile appliance.
There is, however, a need in the art to obviate the deficiencies in the prior art and provide methods that use uplink and/or downlink signal measurements in an exemplary communications network, such as, but not limited to, a UMTS, an LTE network, etc. There is also a need in the art to provide the core measurements necessary for OTDOA positioning methods while attaining the accuracy standards that meet FCC Phase I and II requirements.